Processes for producing branched compounds via condensation and hydrogenation

ABSTRACT

Processes for producing branched compounds are described wherein a carbonyl compound is condensed in the presence of a catalyst selected from the group consisting of acids and bases, to form an α,β-unsaturated condensation product; and the α,β-unsaturated condensation product is hydrogenated.

BACKGROUND OF THE INVENTION

Guerbet alcohols are primary alcohols branched in the 2-position whichare obtained by condensation of linear fatty alcohols. The products aremainly used as oil components for the production of cosmetic emulsions.They are generally produced from fatty alcohols which, initially,self-condense under the effect of strong bases and heavy metalcompounds, for example copper or zinc oxide. It is assumed that, underthe reaction conditions, the alcohol is first dehydrogenated to thealdehyde which enters into an aldol condensation with itself, afterwhich the condensation product is hydrogenated to the alcohol. Acorresponding overview can be found, for example, in Angew. Chem. 64,212 (1952). Dialkyl cyclohexanes are similarly produced by doublecondensation of fatty alcohols with cyclohexanol in the presence ofheavy metals.

However, a disadvantage is that, after the reaction, the heavy metalcatalysts have to be removed in order to meet legal requirements and toensure that they do not cause any irritation in the subsequentapplication. The heavy metal catalysts are generally removed by washingand subsequent distillation which involves considerable product losses.Another disadvantage is that the reaction times are very long and theselectivities are unsatisfactory.

BRIEF SUMMARY OF THE INVENTION

The present invention relates, in general, to cosmetic oil componentsand, more particularly, to an improved process for the production of,for example, Guerbet alcohols and dialkyl cyclohexanes which does notrequire heavy metal catalysts for the condensation reaction and whichcombines improved selectivity with a higher reaction rate.

It has surprisingly been found that branched alcohols or branchedhydrocarbons can be obtained by the process according to the inventionwithout the use of heavy metal catalysts in the condensation reaction,both improved selectivities and higher reaction rates being obtained.

DETAILED DESCRIPTION OF THE INVENTION

Carbonyl Compounds

Suitable carbonyl compounds are, above all aldehydes, ketones andmixtures thereof. Suitable aldehydes are, for example, fatty aldehydeswhich preferably correspond to formula (I):R¹CHO  (I)in wich R¹ is a linear or branched alkyl group containing 6 to 12 andmore particularly 8 to 10 carbon atoms. Typical examples are hexanal,octanal, 2-ethylhexanal, decanal, dodecanal and mixture thereof. Alsosuitable are fatty ketones, preferably those corresponding toformula(II):R²COR³  (II)in which R² and R³ independently of one another represent linear orbranched C₆₋₁₂ alkyl groups. Typical examples are dihexyl ketone,dioctyl ketone, di-2-ethylhexyl ketone, didecyl ketone or didocelketone. Cyclic ketones, preferably cyclohexanone, may also be used.Condensation

The condensation reaction may be carried out in known manner, i.e. thecarbonyl compounds are initially introduced into the reactor togetherwith the acids or bases and then heated to temperatures of 20 to 250° C.and preferably to temperatures of 200 to 240° C. The reaction may becarried out in the absence of pressure or under pressures of up to 30bar and preferably up to 5 bar. Suitable catalysts are, in particular,alkali metal bases such as, for example, alkali metal hydroxides oralkali metal carbonates. The catalysts may be used in quantities of 1 to10 mol-% and are preferably used in quantities of 3 to 5 mol-%, based onthe carbonyl compounds. In order to displace the reaction equilibriumonto the product side, it is always advisable continuously to distil offthe water of condensation.

Hydrogenation

The hydrogenation of the unsaturated aldehydes or ketones formed as theintermediate product may be carried out using typical hydrogenationcatalysts, preferably based on nickel, copper and/or zinc. Thehydrogenation is normally carried out at temperatures of 20 to 350° C.and preferably at temperatures of 50 to 250° C. and under pressures of 1to 300 bar and preferably under pressures of 20 to 250 bar. The reactionproducts may then be purified by distillation.

EXAMPLES Example 1

In a stirred reactor consisting of a flask, heating mushroom, waterseparator, reflux condenser and nitrogen inlet, 1 g (0.015 mol) ofpotassium hydroxide was added to 500 g (3.2 mol) of decanal (99% byweight) at 20° C., followed by heating to 210° C. The water formedduring the reaction was continuously distilled off. After 3 hours, thereaction was terminated, the reaction mixture was cooled to 20° C. andthe potassium hydroxide precipitated was filtered off. The resultingclear liquid contained 90% by weight of α,β-unsaturated aldehyde, 4% byweight trimers, 2% by weight esters and 4% by weight unreacted startingaldehyde. The reaction mixture was transferred to an autoclave andhydrogenated for 3 hours at 230° C./250 bar in the presence of a nickelcatalyst until there was no further uptake of hydrogen. 90% by weight ofthe hydrogenation product consisted of 2-octyl dodecanol, 6% by weightof decanol and 4% by weight of trimers. After distillation, the 2-octyldodecanol was obtained in a purity of 95.7% by weight.

Example 2

As in Example 1, 500 g (3.9 mol) of octanal were condensed in thepresence of 1.2 g (0.02 mol) of potassium hydroxide. The resultingproduct contained 88% by weight of α,β-unsaturated aldehyde, 6% byweight of trimers, 2% by weight of waters and 4% by weight of unreactedoctanal. After hydrogenation, a mixture of 88% by weight of 2-hexyldecanol, 6% by weight of octanol and 6% by weight of trimers wasobtained. After distillation, the 2-hexyl decanol was obtained in apurity of 93.6% by weight.

Example 3

As in Example 1, 650 g (5.0 mol) of 2-ethyl hexanal and 245 g (2.5 mol)of cyclohexanone were condensed in the presence of 40 g of 45% by weightaqueous potassium hydroxide solution. After 2 hours, the reactiontemperature of 240° C. was reached, the end point being indicated by theend of the separation of water. The product was washed with hot wateruntil neutral and dried with sodium sulfate. According to GC analysis, amixture of 85.4% by weight of disubstituted product, 8.2% by weight ofmonosubstituted product, 1.3% by weight of 2-ethyl hexanal, 0.3% byweight of cyclohexanone and 4.8% by weight of polymers was present. 500g of the mixture were hydrogenated for 14 hours at 245° C./20 bar in thepresence of 14 g of a nickel catalyst until there was no further uptakeof hydrogen. Wet-chemical analysis of the product revealed an acid valueof <0.1, an iodine value of 0.4 and a hydroxyl value of 1. GC analysisshowed the composition to be 85.4% by weight2,6-di-(2-ethylhexyl)-cyclohexane, 8.2% by weight2-(2-ethylhexyl)-cyclohexane, 1.3% by weight 2-ethyl hexane, 0.3% byweight cyclohexane and 4.8% by weight oligomers. The unreacted startingmaterials were removed by distillation.

1. A process for producing branched compounds, comprising the steps of:(a) condensing at a temperature from 210° C. to 250° C. a carbonylcompound comprising an aldehyde of the general formula (I):R¹CHO  (I) wherein R¹ represents an alkyl group having from 6 to 12carbons atoms, and/or a ketone of the general formula (II):R²COR³  (II) wherein R² and R³ each independently represent an alkylgroup having from 6 to 12 carbon atoms, in the presence of an alkalimetal base catalyst to form an α,β-unsaturated condensation product; and(b) hydrogenating the α,β-unsaturated condensation product.
 2. Theprocess according to claim 1, wherein the alkali metal base is selectedfrom the group consisting of alkali metal hydroxides and alkali metalcarbonates.
 3. The process according to claim 2, wherein the alkalimetal base is an alkali metal hydroxide.
 4. The process according toclaim 2, wherein the alkali metal base is an alkali metal carbonate. 5.The process according to claim 1, wherein the carbonyl compoundcomprises a cyclic ketone.
 6. The process according to claim 1, whereinthe hydrogenation is carried out at temperature of from 20 to 350° C. 7.The process according to claim 1, wherein the hydrogenation is carriedout in the presence of a catalyst selected from the group consisting ofnickel, copper and zinc compounds.
 8. The process according to claim 6,wherein the hydrogenation is carried out in the presence of a catalystselected from the group consisting of nickel, copper and zinc compounds.9. The process according to claim 1, wherein the hydrogenation iscarried out at a pressure of from 1 to 300 bar.
 10. The processaccording to claim 1, further comprising distilling the hydrogenatedcondensation product.
 11. The process according to claim 1, wherein thecondensation is carried out in a heavy metal-free reaction medium.